The present invention relates to a display controller, a display system, and a display control method.
In recent years, a display device using an electroluminescent (EL) element has attracted attention. In particular, since an organic EL panel including an EL element formed using a thin film of an organic material is a self-emission type, a backlight becomes unnecessary, whereby a wide viewing angle is realized. Moreover, since the organic EL panel has a high response speed in comparison with a liquid crystal panel, a color video display can be easily realized using a simple configuration.
The organic EL panel is divided into a simple matrix type and an active matrix type in the same manner as the liquid crystal panel. When driving a simple matrix type organic EL panel, grayscale control may be performed using pulse width modulation (hereinafter abbreviated as “PWM”). A display controller outputs display data supplied from a host to a driver which drives the organic EL panel at a predetermined read timing, and performs grayscale control by outputting display control signals.
As described above, the EL element which makes up the organic EL panel has a high response speed in comparison with a liquid crystal element which makes up the liquid crystal panel. Therefore, while the refresh rate of the liquid crystal panel is 60 Hz, the refresh rate of the organic EL panel is 160 Hz, for example. Therefore, it is necessary for a data driver which drives the organic EL panel to read the display data 160 times per second and to drive data lines of the organic EL panel based on the display data, for example.
However, when displaying a video image, it suffices that the display image be changed at a rate of 15 Hz or 20 Hz which is suitable for the human eye. In this case, the data driver can display a video image at 16 Hz by repeatedly using the same display data 10 times, for example.
The display controller which supplies the display data or the like to the data driver includes a frame memory which stores the display data for one vertical scan period for example, and the display data from the host is stored in the frame memory. Since the host cannot rewrite the display data for one frame (one vertical scan period) at a rate of 160 Hz, the host counts the number of frames and supplies the display data to the display controller in a predetermined frame cycle. Therefore, an additional processing load is imposed on the host.